X-ray inspection system

ABSTRACT

The X-ray inspection system  10  comprises an X-ray electron conversion face  42  for converting an entered X-ray image transmitted through the measurement object into an electronic image, an output fluorescent face  46  for emitting fluorescence when an electronic image is entered, and deflecting means  44  which is installed between the X-ray electron conversion face  42  and output fluorescent face  46 , wherein the electronic image which was entered and converted at the X-ray electron conversion face  42  is converged into a predetermined area on the output fluorescent face  46  by the deflecting means  44  so as to make the X-ray fluoroscopic image of the moving measurement object stand still on the output fluorescent face  46 . By this, the image of the measurement object can be captured during the time when the X-ray fluorescence image is standing still, so sensitivity can be secured while increasing the resolution.

TECHNICAL FIELD

The present invention relates to an x-ray inspection system forinspecting a measurement object based on the X-ray fluoroscopic image ofthe measurement object which is moving at a predetermined speed, andmore particularly to an in-line non-destructive inspection system forinspecting a measurement object which is being carried by a beltconveyor.

BACKGROUND ART

X-ray inspection systems using X-rays have been known as systems forinspecting the internal state of a measurement object non-destructively.The X-ray inspection system irradiates an X-ray, which is output beingdiverged from one point of the X-ray source in a predetermined angledirection, onto the measurement object, and capturing the image of theX-ray which transmitted through the measurement object using an X-rayimage capturing unit, so as to inspect the internal status of themeasurement object.

Japanese Patent Laid-Open No. 11-108858 discloses an X-ray inspectionsystem which inspects a plurality of measurement objects which move on aline, such as a belt conveyor, one after another, using the abovementioned X-ray inspection system. An object of this X-ray inspectionsystem is to obtain a clear X-ray fluoroscopic image while capturing theX-ray image of the moving measurement object. In other words, when themeasurement object passes on a line between the X-ray source and X-rayimage capturing unit, a gate signal is sent to the X-ray image capturingunit, operation of the X-ray image capturing unit is controlled by thisgate signal, and an X-ray fluoroscopic image is captured at the momentwhen the measurement object crosses between the X-ray source and X-rayimage capturing unit.

DISCLOSURE OF THE INVENTION

The above mentioned X-ray inspection system, however, has a problem interms of sensitivity. In other words, as the moving speed of themeasurement object increases, the image capturing time by the X-rayimage capturing unit must be decreased to obtain the requiredresolution, but if the image capturing time decreases, the quantity oftransmitted X-rays received by the X-ray image capturing unit inevitablydecreases, and sensitivity drops.

With the foregoing in view, it is an object of the present invention tosolve the above problem and to provide an X-ray inspection system whichcan implement both the required resolution and sufficient sensitivity inthe X-ray image capturing of the moving measurement object.

An X-ray inspection system according to the present invention comprisesan X-ray source for irradiating an X-ray onto a moving measurementobject, an X-ray image capturing unit which has an X-ray electronconversion face for converting the entered X-ray image corresponding tothe measurement object into an electronic image, and an output facewhere the electronic image emitted from the X-ray electron conversionface enters and the X-ray fluoroscopic image of the measurement objectcorresponding to the entered electronic image is output, positiondetecting means for detecting the position of the measurement object,and deflecting means for deflecting the flow of the electronic imagefrom the X-ray electron conversion face to the output face, forming anelectronic image on a predetermined area on the output face based on theposition of the measurement object detected by the position detectingmeans.

By providing a deflecting means between the X-ray electron conversionface and the output face in this way, the progressing direction of theelectronic image, which is converted by the X-ray electron conversionface and is emitted, can be deflected based on the position of themeasurement object. As a result, even when the X-ray which transmittedthrough the moving measurement object enters a different position of theX-ray electron conversion face, an X-ray fluoroscopic image can beformed on a predetermined area of the output face.

The above mentioned X-ray inspection system may be characterized in thatthe X-ray source is a pulse X-ray source which outputs an X-ray when themeasurement object is within the image capturing range of the X-rayimage capturing unit. By using a pulse X-ray source in this way, theX-ray dose onto the moving measurement object can be decreased. If anX-ray is output only when the measurement object is within the imagecapturing range, the output of X-rays, which has the risk of having anegative influence on the human body, can be controlled.

The above mentioned X-ray inspection system may be characterized in thatthe X-ray image capturing unit further comprises an electrode whichcontrols the flow of electronic images to the output face by applying avoltage between the X-ray electron conversion face and output face. Bycomprising an electrode which controls the flow of electronic images tothe output face in this way, the image capturing time for themeasurement object by the X-ray image capturing unit can be controlled.By this, the resolution of the X-ray fluoroscopic image of the movingmeasurement object can be improved.

The above mentioned X-ray inspection system may be characterized in thatthe X-ray image capturing unit further comprises an electrode whichcontrols the flow of electronic images to the output face by applyingvoltage between the X-ray electron conversion face and output face, theelectrode cancels the control of the flow of electronic images after anX-ray is output from the pulse X-ray source, and controls the flow ofelectronic images before the output of an X-ray from the pulse the pulseX-ray source is stopped. By controlling the flow of electronic images bythe voltage to be applied between the X-ray electron conversion face andoutput face using the electrode, it can be controlled such that theX-ray image capturing unit does not capture an image in an unstablesection which is generated at the rise or fall of the pulse X-ray, sothat images can be captured by an X-ray with stable intensity.

The above mentioned X-ray inspection system may be characterized in thatthe X-ray source is a point light source, and the output face is afluorescent face which emits fluorescence by the entry of electronicimages.

The above mentioned X-ray inspection system may be characterized in thatthe position detecting means further comprises measurement objectdetecting means for detecting the measurement object before reaching theimage capturing range of the X-ray image capturing unit, and theposition of the measurement object in the image capturing range isdetermined based on the detection of the measurement object by themeasurement object detecting means and the elapsed time from the timewhen the measurement object is detected. By detecting the measurementobject which is moving in a predetermined direction at a predeterminedspeed using the measurement object detecting means before themeasurement object reaches the image capturing range of the X-ray, theposition of the measurement object in the X-ray image capturing rangecan be easily calculated from the detection time and elapsed time.

The above mentioned X-ray inspection system may be characterized in thatthe measurement object detecting means further comprises one lightemitting element which emits light onto the measurement object and twolight receiving elements which are installed at different locations andwhich receive light output from the light emitting element, and thedistance between the moving path of the measurement object and the lightemitting element is detected from the time interval of the time when thelight output from the light emitting element to each light receivingelement is blocked by the measurement object. By receiving light outputfrom one light emitting element at the two light receiving elementsinstalled at different locations and by detecting the time when themeasurement object is detected by each light receiving element asdescribed above, the distance between the moving path of the measurementobject which is moving in a predetermined direction at a predeterminedspeed and the light emitting element can be easily calculated.

The above mentioned X-ray inspection system is an X-ray inspectionsystem comprising an X-ray source and X-ray image capturing unit whichare installed facing each other, sandwiching the measurement objectpassing path, wherein the X-ray image capturing unit further comprisesan X-ray electron conversion material, and an output fluorescent facewhich is installed facing the X-ray electron conversion material, andthe X-ray image capturing unit deflects the flow of electronic imagesbetween the X-ray electron conversion material and the outputfluorescent face at a speed synchronizing with the moving speed of themeasurement object.

Since the flow of electronic images between the X-ray electronconversion material and the output fluorescent face is deflected at aspeed synchronizing with the moving speed of the measurement object, theimage capturing time of the measurement object P can be increased,therefore both the required resolution and sufficient sensitivity can beimplemented. Also it is preferable that the above mentioned X-rayinspection system starts deflection according to a predeterminedtrigger, which is generated based on the position of the measurementobject.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram depicting an X-ray inspection system accordingto the first embodiment;

FIG. 2 is a cross-sectional view depicting the X-ray gate I•I;

FIG. 3A, FIG. 3B and FIG. 3C are diagrams depicting the change of theelectron orbit;

FIG. 4 is a diagram depicting the control of current to conduct throughthe deflection coil;

FIG. 5 is a diagram depicting the method of calculating position by theposition detecting means;

FIG. 6 is a timing chart depicting control by the timing circuit;

FIG. 7 is a diagram depicting signals at the pulse X-ray source,deflection circuit and X-ray gate I•I;

FIG. 8 is a diagram depicting the relationship between the deflectiondistance and exposure time;

FIG. 9 is a block diagram depicting an X-ray inspection system accordingto the second embodiment;

FIG. 10 is a timing chart depicting control by the timing circuit;

FIG. 11 is a diagram depicting signals at the pulse X-ray source,deflection circuit and X-ray gate;

FIG. 12 is a block diagram depicting an X-ray inspection systemaccording to the third embodiment;

FIG. 13 is a timing chart depicting control by the timing circuit;

FIG. 14 is a diagram depicting the pulse X-ray source, deflectioncircuit and X-ray gate;

FIG. 15 is a diagram depicting the X-ray inspection system;

FIG. 16 is a diagram depicting the X-ray inspection system; and

FIG. 17 is a timing chart depicting the deflection current to besupplied to the X-ray inspection system X-ray gate I•I 40 and gatesignals.

BEST MODES FOR CARRYING OUT THE INVENTION

Embodiments of the X-ray inspection system according to the presentinvention will now be described in detail with reference to theaccompanying drawings. In the description of the drawings, the sameelements are denoted by the same symbol, where redundant descriptionsare omitted.

FIG. 1 is a block diagram depicting the X-ray inspection system 10 ofthe present embodiment. The X-ray inspection system 10 is used forinspecting the tablets (measurement objects) P which are placed on abelt conveyor 12 and which are moving in a predetermined direction. TheX-ray inspection system 10 is comprised of a belt conveyor 12 fortransporting the placed tablets P at a predetermined speed V, a pulseX-ray source 14 for irradiating the pulse X-rays onto the tablets P onthe belt conveyor 12, an X-ray gate image intensifier (hereafter “X-raygate I•I”) 40 which faces the pulse X-ray source 14, sandwiching thebelt conveyor 12, a CCD camera 18 for capturing X-ray fluorescent imagesobtained by the X-ray gate I•I 40, and a processing judgment device 28for judging the acceptance of the tablets P based on the captured X-rayfluorescent images and performing such processing as sorting. Betweenthe X-ray gate I•I 40 and the CCD camera 18, a lens 16 for forming theX-ray fluorescent images obtained by the X-ray gate I•I 40 at the lightreceiving section of the CCD camera 18 is installed.

The measurement object detecting means 30 is installed at the upstreamof the belt conveyor 12 in the image capturing range where the X-rayimage is captured. The measurement object detecting means 30 iscomprised of a light emitting diode 32 which emits light onto thetablets P on the belt conveyor 12, and two photo-diodes 34 and 36 whichare disposed in parallel with the belt conveyor 12, sandwiching the beltconveyor 12. The two photo-diodes 34 and 36 are connected to the timingcircuit 20. By these, the timing circuit 20 can calculate the positionof the tablet P moving at a predetermined speed V based on the time whenthe photo-diodes 34 and 36 detected the tablet P and the elapsed timefrom the detection time.

The timing circuit 20 is connected to the X-ray power supply 22 forcontrolling an X-ray which is output from the pulse X-ray source 14,X-ray gate power supply 26 which opens/closes the gate of the X-ray gateI•I 40, and deflection circuit 24 for controlling the deflection coil 44which is installed surrounding the X-ray gate I•I 40, and controls therespective operation timing by the timing signals.

Since the time when the tablet P arrives in a space between the X-raysource 14 and the X-ray gate I•I 40 can be determined, deflection can bestarted synchronizing with the arrival time, and the flow of electronicimages can be deflected synchronizing with the moving speed of thetablet P. In other words, the output of the timing circuit 20 is apredetermined trigger which is generated based on the position of thetablet P, and the above mentioned deflection is started according tothis trigger.

Now the X-ray gate I•I 40 will be described. FIG. 2 is a cross-sectionalview depicting the X-ray gate I•I 40. The X-ray gate I•I 40 is comprisedof the X-ray electron conversion face 42 which converts the enteredX-ray images into electronic images, and the output fluorescent face 46which emits fluorescence when an electronic image enters, which aresealed in a container 49 in which pressure is reduced almost to avacuum. An accelerating electrode 48 is installed around the inner wallof the container 49, and by controlling the voltage to be applied to theaccelerating electrode 48, the gate of the X-ray gate I•I 40 can becontrolled. In other words, if the output fluorescent face 46 side hashigh potential, the electronic images flowing from the X-ray electronconversion face 42 to the output fluorescent face 46 are accelerated,and if, on the other hand, the output fluorescent face 46 side has lowpotential, the flow of the electronic images from the X-ray electronconversion face 42 to the output fluorescent face 46 is controlled.

Next operation of the X-ray inspection system 10 will be described. Thetablets P, which are the measurement objects, are placed on the beltconveyor 12 and are moving to the right in FIG. 1 at a predeterminedspeed V. When the tablet P blocks light which is output from the lightemitting diode 32 to the first photo-diode 34, the time (hereafter“first light blocking time”) is transmitted from the first photo-diode34 to the timing circuit 20. When the tablet P is transported by thebelt conveyor 12 and blocks the light which is output from the lightemitting diode 32 to the second photo-diode 36, the time (hereafter“second light blocking time”) is transmitted from the second photo-diode36 to the timing circuit 20.

The timing circuit 20 detects the position of the table P based on thesecond light blocking time transmitted from the second photo-diode 36.In other words, the transporting speed V of the belt conveyor 12 ispredetermined, so the timing circuit 20 can calculate the currentposition of the tablet P based on the second light blocking time and theelapsed time from the second light blocking time. And based on thispositional information, that is, the elapsed time from the second lightblocking time, the timing circuit 20 outputs the timing signal to thepulse X-ray power supply 22, deflection circuit 24, and X-ray gate powersupply 26, for control.

Now control of the deflection coil 44, which is a characteristic of thepresent embodiment, will be described with reference to FIG. 3A, FIG. 3Band FIG. 3C depicting the relationship of the deflection current to beconducted to the deflection coil 44 and the electron orbit. In FIG. 3A,FIG. 3B and FIG. 3C, the deflection coil 44 is shown inside thecontainer 40 to clarify the conduction direction of the deflectioncurrent, where the moving direction of the tablet P is the X axis, theline connecting the pulse X-ray source 14 and the center of the X-rayelectron conversion face 42 of the X-ray gate I•I 40 is the Y axis, andthe axis from the back to the front of the page face is the Z axis, andthe intersection of the X axis, Y axis and Z axis is the origin 0. FIG.3A, FIG. 3B and FIG. 3C are diagrams depicting the states of the tabletP transported by the belt conveyor 12 passing the origin 0 in a timeseries.

As FIG. 3A shows, when the tablet P is in the negative area of the Xaxis (upper side of the Y axis in FIG. 3A), the X-ray image transmittedthrough the tablet P enters the negative area of the X axis on the X-rayelectron conversion face 42. When the X-ray image enters the X-rayelectron conversion face 42, an electronic image is emitted from theX-ray electron conversion face 42, and the emitted electronic image isaccelerated by the accelerating electrode 48, and enters the outputfluorescent face 46. In this process, as FIG. 3A shows, current flowingin the counterclockwise direction, shown in FIG. 3A, is conducted to thedeflection coil 44, so as to generate the magnetic field B in the Z axisdirection. By this, the electronic image flowing from the X-ray electronconversion face 42 to the output fluorescent face 46 shifts from themagnetic field B in the X axis direction by receiving Lorentz's force,and enters roughly the center of the output fluorescent face 46.

As FIG. 3B shows, when the tablet P moves and the tablet P comes to theorigin 0, the transmitted X-ray image of the tablet P enters the centerof the X-ray electron conversion face 42. In this case, it isunnecessary to generate the magnetic field B, and the electronic imageemitted from the X-ray electron conversion face 42 enters the center ofthe output fluorescent face 46 as is.

As FIG. 3C shows, when the tablet P moves more and is in the positivearea of the X axis (lower side of the Y axis in FIG. 3A), thetransmitted X-ray image of the tablet P enters the positive area of theX axis on the X-ray electron conversion face 42. In this case, contraryto the case of FIG. 3A, current flowing in the clockwise direction,shown in FIG. 3C, is conducted through the deflection coil 44, and themagnetic field B in the negative direction of the Z axis is generated,so that the electronic image is deflected in the negative direction ofthe X axis, to enter the electronic image roughly at the center of theoutput fluorescent face 46.

To generate the magnetic fields shown in FIG. 3A, FIG. 3B and FIG. 3C,the current to be conducted through the deflection coil 44 is as shownin FIG. 4, where the clockwise direction shown in FIG. 3A, FIG. 3B andFIG. 3C is “+”. In other words, current in the “−” direction isconducted through the deflection coil 44 at time t2, and the amount ofcurrent is decreased as the tablet P approaches the origin 0. This is todecrease the amount of deflection as the tablet P approaches the origin0. And at time t4 when the tablet P passes through the origin 0, thedirection of the current is inverted, and is then controlled such thatthe amount of current is increased as the tablet P moves away from theorigin 0. Then at time t6, the current is shut down to 0.

The current value to be conducted through the deflection coil 44 at thistime is a value for deflecting the electronic image output from theX-ray electron conversion face 42, forming the X-ray fluoroscopic imageat the center of the output fluorescent face 46. Therefore the amount ofcurrent to be conducted through the deflection coil 44 changes accordingto the position of the transmitted X-ray image, which enters the X-rayelectron conversion face 42.

Since the pulse X-ray source 14 is a point light source, the position ofthe transmitted X-ray image to be projected onto the X-ray electronconversion face 42 is changed not only by the position of the tablet Pin the X axis direction, but also by the position of the tablet P in theY axis direction.

In the present embodiment, the position of the tablet P in the X axisdirection is calculated by the elapsed time from the second lightshielding time, but the position of the tablet P in the Y axisdirection, that is, the distance from the pulse X-ray source 14, canalso be detected since the first light blocking time is also acquired,and as a result, the position and the moving speed of the X-ray image,which transmits through the tablet P and enters the X-ray electronconversion face 42, can be calculated. This aspect will now be describedwith reference to FIG. 5. As FIG. 5 shows, the positional relationshipof each element constituting the measurement object detecting means 30is that the first photo-diode 34 and the second photo-diode 36 aredisposed in parallel with the moving direction of the tablet P separatedfrom each other at distance d, and the distance between the lineconnecting each light receiving face of the two photo-diodes 34 and 36and the light emitting diode 32 is D.

If the interval between the first light blocking time and the secondlight blocking time in this state is Δt, then the moving distance of thetable P during this time is VΔt. Using the similar relationship of thetriangles, the space between the locus of the tablet P and the lightemitting diode 32 is calculated asX=D×VΔt/d  (1)If the pulse X-ray source 14 and the X-ray gate I•I 40 are disposed atthe positions corresponding to the light emitting diode 32 and thephoto-diodes 34 and 36 shown in FIG. 5, then the moving speed V′ of thetransmitted X-ray image which enters the X-ray electron conversion face42 isV′=V×D/X  (2)and substituting (1) for (2)V′=d/Δtis calculated. Based on this result and on the elapsed time from thesecond light blocking time, the position of the X-ray image, whichtransmits through the tablet P and enters the X-ray electron conversionface 42, can also be calculated, so the amount of current to beconducted through the deflection coil 44 can be controlled.

In this way, by controlling the current to be conducted through thedeflection coil 44 and generating the magnetic field B for deflectingthe electron orbit, the X-ray fluoroscopic image to be projected ontothe output fluorescent face 46 always enters at the center of the outputfluorescent face 46 when the tablet P passes through the origin 0, andduring this time, the X-ray fluoroscopic image of the tablet P looks asif it is standing still at the center of the output fluorescent face 46.

Now the timing signals, which are output from the timing circuit 20 tothe X-ray power supply 22, deflection circuit 24, and X-ray gate powersupply 26, will be described. The X-ray power supply 22, deflectioncircuit 24 and X-ray gate power supply 26 are all controlled based onthe elapsed time from the second light blocking time t0. FIG. 6 is achart depicting the respective timing.

As FIG. 6 shows, at time t0, the tablet P is detected by the secondphoto-diode 36, and the signal 70 from the second photo-diode 36 to thetiming circuit 20 turns ON. The timing circuit 20 calculates time t3when the tablet P enters the image capturing range, and calculates timet5 when the tablet P leaves the image capturing range, since thetransporting speed V of the belt conveyor 12 is constant, and the timingcircuit 20 turns the timing signal 73 to the X-ray gate power supply 26ON when the tablet P is within the image capturing range, that is,applies voltage such that the output fluorescent face 46 side becomeshigh potential by the accelerating electrode 48, and captures the X-rayfluorescence image of the tablet P. And the timing circuit 20 turns thetiming signal 71 from the timing circuit 20 to the X-ray power supply 22ON at time t1, which is before time t3, to output an X-ray from thepulse X-ray source 14, and turns the timing signal 72 from the timingcircuit 20 to the deflection circuit 24 ON at time t2, which issomewhere between time t1 and time t3, to conduct the current to thedeflection coil 44.

FIG. 7 shows the change of X-ray intensity which is output from thepulse X-ray source 14 at this time, and the change of current whichflows through the deflection coil 44. The X-ray intensity 81, afterbeing output from the pulse X-ray source 14 at time t1, rises rapidlyand roughly stabilizes at around the maximum intensity of the X-ray, andthen decreases toward time t7 when the output of the X-ray is stopped.The amount of current 82 which flows through the deflection coil 44deflects at around time t2, when current begins to flow and at time t7when the current is stopped, but basically changes occur linearly withrespect to the time axis from time t2 to time t6.

Since the X-ray which is output from the pulse X-ray source 14 does nothave a perfect pulse form, but has rise and fall portions and currentwhich flows through the deflection coil 44 is deflected at the start andend of X-ray output, so an accurate image cannot be captured duringthese times.

In the X-ray inspection system of the present embodiment, the X-ray gateI•I 40 is used, and the gate of the X-ray gate I•I 40 is opened tocapture the X-ray fluorescopic image of the tablet P when the current,which flows through the pulse X-ray power supply 14 and deflection coil44, is stable, that is, during the time from time t3 to t5. By this, asFIG. 7 shows, the dose of X-ray 83, which enters through the X-ray gateI•I 40, can have roughly a pulse form. For the deflection current 82 aswell, deflection distortion, which is generated at the start and end ofdeflection, can be avoided.

The X-ray fluoroscopic image acquired by the X-ray gate I•I 40 iscaptured by the CCD camera 18, and is sent to the processing judgmentdevice 28. The processing judgment device 28 performs such processing asselecting the tablet P based on the captured X-ray fluoroscopic image.

In the X-ray inspection system 10 of the present embodiment, thedeflection coil 44 is installed in the X-ray gate I•I 40, the orbit ofthe electronic image which is emitted from the X-ray electron conversionface 42 is deflected, so as to form an image roughly at the center ofthe output fluorescent face 46, without depending on the position of thetablet P. As a result, the image of the moving tablet P can be stoodstill on the output fluorescent face 46 and captured, so an exposuretime can be secured and sensitivity can be increased even if the movingspeed of the tablet P is increased.

This aspect will now be described based on the concrete example shown inFIG. 8. In the X-ray inspection system 10 shown in FIG. 8, the tablet P,placed on the belt conveyor 12, is moving to the right in FIG. 8 atspeed 1 (m/s). The tablet P moves on the line which divides the linebetween the pulse X-ray source 14 and the X-ray gate I•I 40 internallyat 1:5, so the transmitted X-ray image of the tablet P, which enters theX-ray electron conversion face 42 of the X-ray gate I•I 40, moves to theright in FIG. 8 at speed 5 (m/s).

In order to capture an image of the tablet P at resolution 0.5 (mm) inthis case, the X-ray gate must be controlled so that the shutter time Tbecomes T=0.5 (mm)/(5000 (mm/s))=1/10000 (s). However, capturing animage at a shutter time of 1 (ms) or less is actually impossible, sincesensitivity is insufficient.

The X-ray inspection system 10 of the present embodiment can deflect theorbit of the electron which is output from the X-ray electron conversionface 42 while the transmitted X-ray image moves for 10 (mm), forexample, on the X-ray electron conversion face 42, so as to make theX-ray image stand still on the output fluorescent face 46. By this, 10(mm)/0.5 (mm)=20 (times), that is, a 2 (ms) sufficient exposure time canbe obtained.

As the above concrete example shows, the X-ray inspection system 10 ofthe present embodiment can secure both the required resolution andsensitivity when the tablet P moving at a high speed is observed.

Now the second embodiment of the present invention will be described.The X-ray inspection system 50 of the second embodiment shown in FIG. 9has basically the same configuration as the X-ray inspection system 10of the first embodiment, but the difference is that the X-ray source 52is used instead of the pulse X-ray source 14.

In the second embodiment, the X-ray source 52 is continuously ON, andthe timing circuit 20 does not control the X-ray power supply 22, asshown in FIG. 10. In other words, the ON signal 71 is constantly inputfrom the power supply circuit, which is not illustrated, to the X-raypower supply 22. The timing circuit 20 turns the timing signal 73 to thedeflection circuit 24 ON at time t2, then turns the timing signal 74 tothe X-ray gate power supply 26 ON at time t3, to capture images. Thismakes control by the timing circuit 20 easier, and a complete pulseX-ray viewed from the X-ray gate I•I 40 can be obtained, as shown inFIG. 11, since an X-ray is output continuously.

Now the third embodiment of the present invention will be described. TheX-ray inspection system 60 of the third embodiment shown in FIG. 12 hasbasically the same configuration as the X-ray inspection system 10 ofthe first embodiment, but the difference is that the X-ray II 62, whichdoes not have a gate function, is used instead of the X-ray gate I•I 40.

In the third embodiment, the X-ray II 62 is continuously ON, and thetiming circuit 20 does not control the X-ray gate, as shown in FIG. 13.In other words, the ON signal 73 is constantly input from the powersupply circuit, which is not illustrated, to the X-ray gate power supply26. And the timing circuit 20 turns the timing signal 72 to thedeflection circuit 24 ON at time t11, and then turns the timing signal71 to the X-ray power supply 22 ON at time t12. This makes control bythe timing circuit 20 easier, and distortion of the deflection current82 can be avoided, as shown in FIG. 14.

The embodiments of the present invention have been described in detail,but the present invention is not limited to the above embodiments.

In the above embodiments, a combination of one light emitting diode 32and two photo-diodes 34 and 36 is used as the measurement objectdetecting means 30 of the tablet P, and the position of the tablet P iscalculated by this measurement object detecting means 30 and elapsedtime, but the detection of the position of the tablet P is not limitedto these embodiments. For example, an image of the tablet P is capturedusing a video camera, and the position of the tablet P, which passesthrough the image capturing range, may be analyzed.

When the moving path of the tablet P is limited to a narrow range, orwhen the moving path of the tablet P is close to the X-ray gate I•I sideand the moving speed of the transmitted X-ray image projected on theX-ray gate I•I does not change much depending on the change of themoving path of the tablet P, the measurement object detecting means maybe a combination of one light emitting diode and one photo-diode.

The above mentioned X-ray inspection system is an X-ray inspectionsystem comprised of an X-ray source 14 and an X-ray image capturing unit40 (16, 18), which are installed facing each other, sandwiching thepassing path of the measurement object P, wherein the X-ray imagecapturing unit 40 has the X-ray electron conversion material 42 and theoutput fluorescent face 46 facing the X-ray electron conversion material42, and the X-ray image capturing unit 40 deflects the flow of anelectronic image between the X-ray electron conversion material 40 andthe output fluorescent face 46 at a speed synchronizing with the movingspeed of the measurement object P.

Since the flow of an electronic image between the X-ray electronconversion material 40 and the output fluorescent face 46 is deflectedat a speed synchronizing with the moving speed of the measurement objectP, the image capturing time of the measurement object P can beincreased, and therefore both the required resolution and sufficientsensitivity can be implemented.

The above mentioned X-ray inspection system starts deflection accordingto a predetermined trigger which is generated based on the position ofthe measurement object P. Since time when the measurement object Parrives in the space between the X-ray source 14 and the X-ray imagecapturing unit 40 can be determined, the deflection is startedsynchronizing with this arrival time, and the flow of an electronicimage is deflected synchronizing with the moving speed of themeasurement object P. In other words, the output of the timing circuit20 is a predetermined trigger which is generated based on the positionof the measurement object P, and the above mentioned deflection isstarted according to this trigger.

In the above mentioned X-ray inspection system, the position of themeasurement object P is detected without contact, and the abovementioned trigger is generated based on the detected position.

This configuration may be such that the position of the measurementobject P is detected using physical contact, and the above mentionedtrigger is generated based on the detected position.

FIG. 15 is a diagram depicting the X-ray inspection system with such aconfiguration, and only the aspects which are different from the abovementioned embodiment are shown. When the measurement object P reaches aspecified position on the belt conveyor 12, the lever L is pressed bythe measurement object P, and the switch S installed on the moving pathof the lever L is turned ON, and the trigger (deflection signal) isoutput synchronizing with this.

The above mentioned X-ray inspection system may comprise restrictingmeans for restricting the position of the measurement object, andreleasing means for releasing the restriction, wherein the abovementioned trigger is generated when a predetermined time has elapsedafter the above mentioned release operation.

FIG. 16 is a diagram depicting the X-ray inspection system with such aconfiguration, and only the aspects which are different from the abovementioned embodiment are shown. When the measurement object P isrestricted at a specified position on the belt conveyor 12 by therestricting means (stopper STP and actuator ACT secured to the stopperSTP), and when the actuator ACT moves up, the stopper is released andfunctions as the releasing means. This releasing operation is executedby the trigger provided from the start controller SCT to the actuatorACT, but the trigger is provided to the X-ray gate I•I 40 as thedeflection signal via the delay circuit DLY. Therefore the trigger tostart deflection is generated when a predetermined time has elapsed fromthe above mentioned release operation. The predetermined time ispre-calculated based on the moving speed of the belt conveyor 12 and thedistance up to the image capturing position.

In the above mentioned X-ray inspection system, deflection maybeperformed independently from the position of the measurement object P.

FIG. 17 is a timing chart of the deflection current and gate signal tobe provided to the deflection coil 44 of the X-ray gate I•I 40 of theX-ray inspection system with such a configuration. The difference fromthe X-ray inspection system shown in FIG. 1 is that deflection isperformed independently from the position of the measurement object P.By flowing the deflection current, which matches the speed of the beltconveyor 12 (specifically, the speed of the X-ray image on thephoto-electric face of the X-ray gate II of the measurement object P)into the deflection coil 44 as the deflection signal, a still image canbe constantly captured. The deflection current has a saw tooth wave. Andthe gate signal of the X-ray gate I•I 40 is turned OFF in the blankingsection of the saw tooth wave. When the gate signal is OFF,the output ofthe X-ray image capturing unit is inhibited. Therefore an even clearerimage can be obtained. For capturing an output image, either themeasurement object P is moved by an interval ({fraction (1/30)} sec.)matching the NTSC system (1 frame per {fraction (1/30)} sec.), or a highspeed camera, for which the image capturing time can be freely set, isused.

In the X-ray inspection systems shown in FIG. 1 and FIG. 2, the X-rayimage capturing unit has a CCD camera 18 which is installed facing theoutput fluorescent face 46, but the position of the measurement object Pmay be detected by its own image capturing mechanism, that is, the CCDcamera 18. When the measurement object P is detected at the edge of theimage output from the CCD camera 18, the image signal constituting thisimage changes, so this signal change is detected and deflection isstarted. The time when the measurement object reaches the position to beimage-captured at the center of the X-ray gate I•I 40, and thedeflection speed synchronizing with the moving can be calculated basedon the moving speed of the belt conveyor 12.

Also in the above mentioned X-ray inspection system, the above mentionedtrigger may be generated by the operator, who visually observes themeasurement object P and turns the switch ON (an equivalent correspondsto the timing circuit 20 in FIG. 1) for starting deflection.

In the above mentioned X-ray inspection system, the belt conveyor 12moves at a constant speed, but this speed may not be constant. In otherwords, if the speed of the belt conveyor 12 is detected in real-time byan encoder, the above mentioned deflection may be performed according tothe moving speed of the measurement object P.

According to the above mentioned X-ray inspection system, the image ofthe moving measurement object can be captured at high sensitivity andhigh resolution by using the X-ray image capturing unit having adeflection function.

Industrial Applicability

The present invention can be applied, to an X-ray inspection systemwhich inspects a measurement object based on the X-ray fluoroscopicimage of the measurement object moving at a predetermined speed,particularly to an in-line non-destructive inspection device forinspecting a measurement object to be transported by a belt conveyor.

1. An X-ray inspection system comprising: an X-ray source forirradiating an X-ray onto a moving measurement object; an X-ray imagecapturing unit which has an X-ray electron conversion face forconverting an entered X-ray image corresponding to said measurementobject into an electronic image and an output face where said electronicimage emitted from said X-ray electron conversion face enters, and anX-ray fluoroscopic image of said measurement object corresponding tosaid entered electronic image is output; position detecting means fordetecting the position of said measurement object; and deflecting meansfor deflecting the flow of said electronic image from said X-rayelectron conversion face to said output face and forming said electronicimage on a predetermined area of said output face based on the positionof said measurement object detected by said position detecting means. 2.The X-ray inspection system according to claim 1, wherein said X-raysource is a pulse X-ray source which outputs the X-ray when saidmeasurement object is within the image capturing range of said X-rayimage capturing unit.
 3. The X-ray inspection system according to claim2, characterized in that: said X-ray image capturing unit furthercomprises an electrode which controls the flow of said electronic imageto said output face by applying a voltage between said X-ray electronconversion face and said output face; and said electrode cancels controlof the flow of said electronic image after the X-ray is output from saidpulse X-ray source, and controls the flow of said electronic imagebefore the output of the X-ray from said pulse X-ray source is stopped.4. The X-ray inspection system according to claim 1, wherein said X-rayimage capturing unit further comprises an electrode which controls theflow of said electronic image to said output face by applying a voltagebetween said X-ray electron conversion face and said output face.
 5. TheX-ray inspection system according to claim 1, wherein said X-ray sourceis a point light source.
 6. The X-ray inspection system according toclaim 1, wherein said output face is a fluorescent face which emitsfluorescence by the entry of said electronic image.
 7. The X-rayinspection system according to claim 1, characterized in that: saidposition detecting means further comprises measurement object detectingmeans for detecting said measurement object before reaching the imagecapturing range of said X-ray capturing unit; and the position of saidmeasurement object in the image capturing range is determined based onthe detection of said measurement object by said measurement objectdetecting means and the elapsed time from the time when said measurementobject is detected.
 8. The X-ray inspection system according to claim 7,characterized in that: said measurement object detecting means furthercomprises one light emitting element which emits light onto saidmeasurement object, and two light receiving elements which are installedat different locations and receive light output from said light emittingelement; and the distance of the moving path of said measurement objectand said light emitting element are detected from the time interval ofthe time when the light output from said light emitting element to eachone of said light receiving elements is blocked by said measurementobject.